Is it permissible for a man to disobey his mother in order to marry another woman, knowing that he is already married and has children, so as to preserve his chastity?

The basic principle is that a man must obey his mother and refrain from marrying you, unless he fears falling into temptation, in which case it is permissible for him to marry to ward off harm from himself. If his mother becomes angry, he should strive to appease her, and he must be just between his wives. It is not permissible for him to marry another woman unless he is able to deal justly between them.